function test_value_filter() {
    add_filter( 'customize_value_custom_css', array( $this, 'filter_value' ), 10, 2 );
    $this->setting->default = '/*default*/';
    $this->assertEquals( '/*default*//*filtered*/', $this->setting->value() );

    $this->factory()->post->create(
      array(
        'post_title'   => $this->setting->stylesheet,
        'post_name'    => $this->setting->stylesheet,
        'post_content' => '/*custom*/',
        'post_status'  => 'publish',
        'post_type'    => 'custom_css',
      )
    );
    remove_theme_mod( 'custom_css_post_id' );
    $this->assertEquals( '/*custom*//*filtered*/', $this->setting->value() );

    $this->wp_customize->set_post_value( $this->setting->id, '/*overridden*/' );
    $this->setting->preview();
    $this->assertEquals( '/*overridden*/', $this->setting->value(), 'Expected value to not be filtered since post value is present.' );
  }